I propose to investigate the effects of testosterone (T) and its metabolites, estradio (E) and 5a-dihydrotestosterone (DHT), on reproductive behavior in male hamsters. Although some behavioral effects of androgenic metabolites have been established, little is known about where in the brain these hormones might act to promote male sexual behavior. In male hamsters, mating is crucially dependent on female-derived chemosensory cues; the vomeronasal and olfactory systems respond to these cues and, through specific nuclei in the amygdala, convey their effects to other parts of the brain. Gonadal steroids may affect sexual behavior in part by acting on the amygdala and other extrahypothalamic sites to influence the way male hamsters respond to these sexually-relevant cues. These extra-hypothalaic effects may then act in concert with andrgenic actions in hypothalamic substrates, particularly the medial prioptic area (MPOA) to facilitate copulation. Specifically my experiments involve brain implants of either T, E, or DHT into the medial nucleus of the amygdala, the bed nucleus of the stria terminalis, the MPOA, and perhaps into the ventromedial hypothalamus and ventral premammillary area, in adult Syrian hamsters. I will assess the effects of these implants on the male's attraction to the female hamster's vaginal secretion (FHVS) in tests where no copulation is permitted and the male cannot make oro-nasal contact with these odor stimuli. To evaluate copulatory behavior I will assess the temporal parameters of mounts, intromissions, and ejaculations, as well as the male:s investigation of different regions of the receptive female's body, including specifically the ano-genital region. Androgens are known to affect both the male's responsibeness to FHVS and copulation with females. These behaviors are absolutely dependent upon specific chemosensory stimuli, and many androgen-concentrating neurons are in locations which would permit them to influence, or be influenced by, the neural pathways utilized by these essential sensory cues. I believe these facts make the male hamster an ideal species for studying many aspects of the hormonal regulation of masculine reproductive behavior.